1. Field of the Invention
The present invention relates to a display controller that outputs a driving signal to a driver circuit of a display part according to display data received from the outside, in particular, a display controller that improves dynamic image displaying performance, and to a display device provided with this display controller.
2. Related Art Statement
In an active matrix liquid crystal display device, display data inputted from an outside system are transformed into gradation voltage, and the gradation voltage is supplied as drain voltage to a liquid crystal panel, realizing gradation displaying. Recently, in the field of such an active matrix liquid crystal display device, a liquid crystal panel is advancing toward a larger screen and higher color purity.
However, a now common TFT liquid crystal material has a response speed of about 20–40 ms. This becomes a main cause of a sense of after-image when a dynamic image is displayed, and, in the present state, satisfactory displaying performance has not been obtained yet. In particular, generally, a response speed of liquid crystal is lower in the case where display changes “from a half tone to a half tone” than in the case where display changes “from white to black” or “from black to white”, sometimes taking a threefold or fourfold time.
As a technique for solving this problem, is known a method for example as shown in Japanese Unexamined Patent Laid-open No. 2000-221475 in which display data for a preceding frame (field) is stored in a memory, and in a next frame, the stored display data is compared with new display data inputted from the outside. Depending on the comparison result, the display data is changed, and gradation display is realized according to the changed display data.
When the above-described technique is employed, response speeds in half tone displaying can be improved, and apparently better displaying quality than before can be obtained.
However, in the above-described technique, display data for one frame should be held always, and further, memory capacity corresponding to two frames is required, since read operation and write operation on the memory should be performed at the same time. This causes problems such as increase of the mounting area of the substrate, increase of the power consumption, increase of the price, and the like.